Electrodeposition process for producing perforated foils with raised portions at the edges of the holes

ABSTRACT

A REPAIRABLE MASTER NEGATIVE AND A PROCESS FOR PRODUCINA G MASTER NEGATIVE SUITABLE FOR THE PRODUCTION OF A NUMBER OF PERFORATED FOILS AND FOR REGENERATING SUCH A MASTER NEGATIVE WHEN IT IS WORN, COMPRISING APPLYING INSULATING MATERIAL TO ONE SURFACE OF A METALLIC BASE PLATE THAT IS STABLE IN A BATH OF AN ALKALI AT SELECTED AREAS THEREOF WHICH CONFORM WITH THE PERFORATIONS IN THE FOILS TO BE PRODUCED, APPLYING A COATING OF A METAL WHICH IS ERODABLE IN A BATH OF AN ALKALI WHICH IS BUILT UP ON THE METALLIC BASE PLATE AFTER THE INSULATING AREAS HAVE BEEN APPLIED TO IT, AND PASSIVATING THE METALLIC COATING WHEN THE MASTER NEGATIVE IS WORN DUE TO THE PRODUCTION OF A NUMBER OF PERFORATED FOILS, IT IS REPAIRED BY STRIPPING OFF ELECTROLYTICALLY IN A BATH OF AN ALKALI THE METALLIC COATING AND A NEW METALLIC COATING IS ELECTRODEPOSITED ON THE METALLIC BASE PLATE WITHOUT DISTURBING THE INSULATED AREAS.

April 10, 1913 B. FUTTERER 3,726,770

ELECTRODEPOSI'I'IUN PROCESS FOR PRODUCING PBkFURATluI) FOH-S WITH RAISEDPORTIONS AT THE EDGES OF THE HOLES Original Filed July 6, 1967 UnitedStates Patent 66 rm. (:1. czsi 5/48; B01k 1/00 US. Cl. 204-16 ClaimsABSTRACT OF THE DISCLOSURE A repairable master negative and a processfor producing a master negative suitable for the production of a numberof perforated foils and for regenerating such a master negative when itis worn, comprising applying insulating material to One surface of ametallic base plate that is stable in a bath of an alkali at selectedareas thereof which conform with the perforations in the foils to beproduced, applying a coating of a metal which is erodable in a bath ofan alkali which is built up on the metallic base plate after theinsulating areas have been applied to it, and passivating the metalliccoating When the master negative is worn due to the production of anumber of perforated foils, it is repaired by stripping olfelectrolytically in a bath of an alkali the metallic coating and a newmetallic coating is electrodeposited on the metallic base plate withoutdisturbing the insulated areas.

This is a continuation of application Ser No. 52,810 filed July 7, 1970and now abandoned, which is a division of application Ser. No. 651,548,filed July 6, 1967, and now abandoned.

The invention relates to an electrodeposition process for producingperforated foils with raised portions at the edges of the holes, as usedin particular for screens and shearing foils of electric shavers.

A process for making perforated foils by electrodeposition is alreadyknown according to which a metal plate serving as a master negative iscovered with an electrically insulating material in the areas of theholes so as to prevent the electrodeposition of the metal thereat; whilethat part of the master negative which is left free from insulatingmaterial and on which the deposit is to be effected is provided byelectroplating with a metal coating the thickness of which is such thatthe areas covered by insulating material are framed to a certain extent,after which the metal coating is passivated.

A process such as this gives a master negative with which a number ofperforated foils can be produced. Thereafter, however, the masternegative must be reprepared, namely by removing the entire surface ofthe master negative down to the metal base plate and then rebuilding it.

in the production of shearing foils for dry shavers, great demands aremade as to the accuracy and the quality of the surface of shearing foilsproduced with a master negative. It has been found that when using amaster negative made by said known process only few shearing foils madewith it are of sufiiciently good quality. Moreover, the repreparation ofa master negative is a relatively costly procedure, since the surface ofthe metal base plate must be ground.

It is an object of the invention to provide a process for producingmaster negatives which may be used repeatedly in the production ofperforated foils with raised edge portions.

A further object of the invention is to provide a process for theproduction of master negatives which is simple to carry out and whichleads to master negatives of great accuracy.

Yet another object of the invention is the provision of a process forthe production of master negatives which enables a simple repreparationof a worn master negative.

Still another object of the invention is to provide a process foreconomically producing perforated foils of outstanding quality, whereina metal base plate stable in a bath of alkali, is covered with anelectrically insulating material, also stable in a bath of alkali in thearea of the holes in order to prevent electrodeposition of metal at thatareas. Thereafter the metal base plate is plated with a coating of ametal which can be stripped off in an electrolytic bath of an alkali,the thickness of the coating being built up such that the insulatedareas are framed. Next the coating is passivated, so that theelectrodeposit of a metal during production of a perforated foil doesnot adhere to the coating.

According to a further object of the invention the base plate is made ofa metal which is not attacked in a bath of an alkali. Among those metalswhich are suitable for this purpose are steel, nickel; and brass.

A further object is to prepare a master negative for the production ofperforated foils With raised edge portions by covering a metal baseplate of a resistant to a bath of an alkali metal at definite areas withan electric insulating material, and thereafter coating the base platewith tin or zinc and passivating said coating after it has been built upto such thickness that the insulated areas are framed by the coating.

Coatings of tin or zinc gives excellent protection of the edges of thepattern of insulating areas and can be stripped off electrolyticallyvery rapidly in a bath of an alkali.

The passivation of the metal coating, which is to prevent any adhesionof the perforated foils which are to be produced may be carried out inany manner known in the art, for example with bichromate solution.

A metal having a lower melting point than the metal of the base platemay be employed for the coating. The metal coating may then be removedby heat instead of electrolytic attack when repreparing the masternegative.

These and other objects of the invention will become apparent from thefollowing description in connection with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view of a plate-shaped master negativeproduced with insulating spots at the upper surface of a metal baseplate; and

FIG. 2 is a view similar to FIG. 1, but with the insulating spotsembedded into the surface of the plate.

To make a master negative which is partly illustrated in FIG. 1, a baseplate 1 of steel, nickel or some other metal which is resistant in bathsof alkalies is covered with a pattern of areas of insulating material,also stable in baths of alkalis, which correspond to the subsequentperforations of the foils produced with the master negative. The spotsof insulating material may be applied to the metal base plate 1 by aphotographic process. The unit is thereafter suspended in an acid tinbath and a tin coating is applied by electroplating the free areas ofthe metal base plate 1. Electroplating is continued until the differencebetween the thickness of the metal coating 3 and the thickness of theinsulating spots 2 corresponds to the desired height of the edges of theholes or perforations. Finally, the surface of the tin coating ispassivated in a bichromate solution and rinsed in clear water.

The master negative produced in this way is then suspended in anelectrolytic bath for depositing a perforated foil 4 of for examplenickel on it. As is illustrated in FIGS. 1 and 2, the finished foil hasa raised portion at each edge of a hole.

The preparation of the master negative which is partly shown in FIG. 2with a foil applied thereon by electrodeposition differs from the methoddescribed above in that the areas of insulating material 2 are embeddedin the surface of the metal base plate, for example by etching the sameand filling in the etched areas with a layer of insulating material 2.

It will be apparent to those skilled in the art that a master negativeproduced in accordance with the invention may be reprepared in a simpleand rapid manner. Further, the master negative may be used to produce asubstantially greater number of perforated foils than the masternegatives produced by known processes.

I claim:

1. A process for producing repairable master negative plates for makingperformated foils by electrodeposition, comprising the steps of ofproviding a base plate made of a metal which is resistant to a bath ofan alkali, forming electrically insulated areas on the base plate in theareas where it is desired to have perforations in the foil with aninsulating material which is resistant to a bath of an alkali,electroplating the uninsulated areas of said base plate with a metalselected from the group consisting of tin and zinc which can bedissolved electrochemically in a bath of an alkali, passivating themetal coating so as to enable a foil electrodeposited on the masternegative plate to be easily stripped therefrom, electrochemicallyremoving said metal coating after it has been damaged from stripping offfoils without removing the insulating areas on the base plate, thenre-electroplating the uninsulated areas of said base plate with a metalwhich can be dissolved electrochemically in a bath of an alkali.

2. A process for producing repairable master negative plates for makingperforated foils by electrodeposition, comprising the steps of providinga base plate made of a metal which is resistant to bath of an alkali,forming electrically insulated areas on the base plate in the areaswhere it is desired to have perforations in the foil with an insulatingmaterial which is resistant to a bath of an alkali, electroplating theuninsulated areas of said base plate with a metal coating, passivatingthe metal coating so as to enable a foil electrodeposited on the masternegative plate to be easily stripped therefrom, said metal coating beinga metal which has a lower melting point than said base plate metal andsaid insulated areas, and removing said metal coating after it has beendamaged by applying heat, then re-electroplat ing the uninsulated areasof said base plate with a metal which has a lower melting point thansaid base plate metal and said insulated area.

References Cited UNITED STATES PATENTS 1,471,469 10/ 1923 Kardos 204-1461,867,527 7/1932 Dunn 204-146 2,200,782 5/ 1940 Vollmer 204-1461,589,564 6/1926 Robinson 204-281 FOREIGN PATENTS 1,160,258 12/1963Germany 204-11 17,918 1892 Great Britain 204-281 1,147,818 4/ 1963Germany 204-11 OTHER REFERENCES Product Engineering, June 5, 1961 pp.609-614, W. H. Safranek.

JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner US. Cl.X.R. 204-11, 146, 281

